Psychology Today has an excellent article in its 'Reality Check' blog titled 'What You Should Know About 2012: Answers to 13 Questions - Is it really time for the Apocalypse?'. It debunks many of the more hysterical rumors and myths that have been circulating about this topic for far too long. Here's an excerpt.
In the late 1960s and 1970s, the Maya calendar ... caught the interest of counterculture hippies who were using psychedelic drugs such as LSD, DMT, psilocybin, and cannabis and who were also interested in astrology (including the "Age of Aquarius"), numerology, Tarot, and the Chinese divinatory practice of the I Ching (Yì Jīng). These included authors Terence McKenna and José Argüelles (one of the creators of the Whole Earth Festival in 1970), who wrote books, taught workshops, and gave lectures describing mystical experiences based on their use of psychedelics. They saw similar patterns in the Maya calendar and the I Ching that suggested to them the 2012 date would be associated with a spiritual "transformation of consciousness," an idea that became popular among people interested in New Age beliefs. In 1975, both McKenna (with his brother Dennis) and Argüelles published books in which they identified 2012 as the year this would happen. However, they did not narrow the date down to December 21, 2012 until 1983, when archaeologist Robert Sharer published that correlation in an appendix to the 4th edition of Sylvanus Morley's classic book The Ancient Maya.
The significance of the date was popularized during a counterculture event known as the Harmonic Convergence that was organized by Argüelles on August 16-17, 1987. Argüelles, who thought that the problems of Western civilization were due to the use of a calendar that was not directly linked to the movements of the Sun, the Moon, the planets, and the stars. He sought to revive a version of the Maya calendar based on solar and lunar cycles, creating a new system that he called the Dreamspell. Following the Maya calendar, it was based on the numbers 13 and 20 rather than 12 and 60. He thought that the use of this different calendar ultimately bring about world peace.
The Harmonic Convergence, which built on the success of Shirley MacLaine's book and TV miniseries Out on a Limb (1986), was promoted using new computer technology (especially the Apple Macintosh, first introduced in January 1984) and early computer networks. Since the 1960s, interest in astrology, Tarot, the I Ching, and the Maya calendar had been widespread among programmers associated with the new personal computer and software industry in what was to become Silicon Valley in northern California. Counterculture and New Age concepts, including those of psychologist Timothy Leary, McKenna, and Arguelles, had been a part of cyberculture since its inception, so it was only natural that early digital social networks of the mid-1980s, such as FidoNet and The WELL, played a role in spreading the word about the Harmonic Convergence and 2012 among psychedelic and computer "hacker" subcultures that frequently overlapped (cannabis and psychedelic users included influential programmers and innovators such as Bill Gates of Microsoft, Steven Jobs of Apple, and many others.) The 2012 mythology emerged from the same counterculture environment of San Francisco and the campuses of UC-Berkeley and Stanford that contributed to significant cultural changes of the 1960s, including radical politics, environmental awareness, and the "liberation of knowledge." It was from this same milieu that came computer and Internet pioneer Doug Englebart (whose inventions included the computer mouse and hypertext) as well as Ken Kesey and the Merry Pranksters (among whom was cyberculture pioneer Stewart Brand) and the Grateful Dead. Its cultural legacy survives today in such phenomena as alternative medicine, environmentalism, ayahuasca therapy, Burning Man, Wikileaks, and the Occupy movement.
There's much more at the link, including many links in the text (omitted in the excerpt above) to explain terms and topics that may not be familiar. Interesting information, and very useful ammunition to debunk any of the myths thrown at you by those who are more interested in pseudo-science and fear-mongering than in fact. Recommended reading.